Flotation process



Jan. 3, 1939. J. D. PRICE 2,142,207

FLoTATfloN PROCESS Filed 0pt, 29, 1955 2 Sheets-Sheet 1 Jan. 3, 1939. J, D. PRICE FLOTATION PROCESS Filed Oct, 29, 1935 2 Sheets-Sheet 2 INVENTOR. JOHN D. P19/CE BY ww a *ATTORNEK `Patented Jan. 3, 1939 UNITED STATES PATENT OFFICE f FLQTATION PROCESS John D Price, Pueblo, Colo., assignor, by mesne assignments, to The Colorado Fuel and Iron Corporation, a corporation of -Colorado Appuaonoctqbe'r 29, 1935, serial No. 47,251

` 26 Claims.

'I'his invention relates to a notation process and system of treating ores, and more particularly relates to a method and means for cleaning coal by flotation.

It is a principal object of the invention to cre of the treatment.

A further object of the invention is the creation of a froth of 'sumcient stability to promote good recovery during the notation treatment, and of sumcient brittleness to render the concentrate readily amenable to a subsequent dewatering treatment.

Still another object of the invention is the provision of a temperature control of the pressure mediums employed in the process.

A still further object of the invention is to subject the material under treatment to a pulsating movement for accelerating the separation of values from gangue.

various metallic suldes being particularly amenable to this treatment. In the froth flotation concentration of coal the same methods have been employed, generally with some variation in the reagent used to promote frothing and collection.

While satisfactory results may be attained by the foregoing methods insofar as the percentage of coal recovered is concerned, considerable difliculty is experienced in dewateringl the concentrate, because of the stability of the froth; and unless a stable froth is produced, the percentage of recovery is not high enough to warrant the expense of the treatment. It has also been proposed to employ a separating vessel operated under partialvacuum for diffusing air throughout the pulp and thereby effecting a recovery of values. A high capacity vacuum pump is required and considerable difiiculty is encountered due to leakage, and these conditions render the process expensive in operation.

'I'he present invention p ermits the concentra- A tion of values in a froth of suiiicient stability to insure high percentage recovery, but of sumcient brittleness to permit de watering of the concentrate by inexpensive methods.

To produce a froth of. this character, the pulp 5 under treatment in a conned state is subjected to pressure by the introduction of a gas under pressure into the pulp body, and subsequently, the pressure is released with the result that gas confined in the pulp body escapes, rising through l0 the same to its upper surface. This pressure release method of frothing effects a fine dispersion of gas throughout the pulp, subjecting the values to substantially constant association with bubbles of the gas until these values are carried to the surface where they collect in a froth.

The velocity of the material under pressure is subject to control prior to the pressure release, and the rate at which the pressure is released is also controlled with the result that no violent agitation occurs from this type of frothing.

The. absence of violence in aerating the pulp permits use of froth of less stable character than would be necessary if violent agitation was used in order to effect a good recovery of values, and consequently smaller amounts of reagent are used than in other processes.

Various. gases may be employed for this purpose, such as air'for example, but particularly effective results are attained when a gas containing a high percentage of C02, such as the gas evolved from a lime kiln, i-lue gas, or any other gas having a higher degree of solubility in water than air.

The reagent of the treatment may consist of mi any of the soluble or insoluble materials commonly used for the flotation of coal, suchas petroleum oils, coal tar oils, coal tar acids, etc.

In the co-pending application of Phillip M. Frantz, Serial No. 586,250, led January 12, 1932 4o for Coal notation process, reagents particularly well suited for coal flotation have been described, and may be eectively employed in the present invention. It is preferred that the reagent be l introduced into the material being treated continuously in measured amounts.

It will be understood that the invention may be vpracticed in various types of apparatus, and to promote a better understanding of the various steps and treatments, the accompanying drawings illustrate apparatus particularly effective in performing the process. ,Y

In the drawings, in the several views of which like parts have been similarly designated, Y v

Figure 1 is a diagrammatic-representation of' the assembly o'f elementsemployed in performing the process; 5

Figure 2' is a diagrammatic representation drawn to a reduced scale, of the application of temperature control means to apparatus for performing the process;

Figure -3 is a diagrammaticl representation drawn to a reduced scale.' of a modification of the reagent feed in the treatment; and

Figure 4 is'a diagrammatic rep'esentation, also drawn to a. reduced scale, of an assembly of elements for subjecting the ore or coal to successive treatments.

Referring now to Figure 1, the reference numeral 5 designates a conditioner for initially preparing the material for treatment. A suitable launder 6 or other means delivers pulp to the conditioner and a reagent feeder 1 is also provided for introducing reagentinto the conditioner. The reagent Vfeeder is preferably of the type which will deliver measured amounts of reagent.

The conditioner is provided with a discharge outlet 8, and agitators 9 in the conditioner thoroughly diffuse the reagent through the pulp prior to its discharge through outlet 8. In this connection, itis to be understood that any other suitable method of conditioning may be employed.

Material passing throughoutlet 8 is delivered into a collecting tank III. The discharge from tank I0 is controlled by suitable means, such asa star feeder I2, and measured amounts of the conditioned pulp are introduced linto a charging vessel I3 by the star feeder l2. .v

'Ihe charging vessel I3 is provided with a suitable float-operated mechanism I4 for controlling a speed regulating mechanism I5, which in turn controls the operation of the star feeder I2.l 'I'he charging device I3 is also provided with a discharge outlet I6 controlled by an adjustable valve I1. The oat-operated mechanism I4 functions to admit as much material Ainto charger i3 as is being dischargedout of the same, andv in this way the liquid level is maintained substantially constant.

'. charger I 3 is represented as comprising a coney I8 operated by a hand wheel I9.

valve I1 carried on a rack and pinion mechanism A pressure gas isi supplied from a suitable source, such as a compressor (not shown) by valve-controlled pipes 20 and 2|. Pipe 20 admits gas into the tank I3 at an elevation above its liquid level while pipe 2l extends into the tank I3 in the form of a perforated distributor 22,

where the pulp passing through outlet I 6 is to.

be subjected to pressure changes of considerable magnitude, the pressure above the liquid body should be muchk in excess of the pressure within said body. A

vAs an example, if gas from a compressor at twenty pounds per square Iinch pressure is introduced into the tank, eiective results will be attained if said gas is maintained at fifteen Ii pounds pressure, above the liquid-level.

'I'he mechanism for controlling the outlot from The pulp, now more oi' less completely saturated with dissolved gas under pressure, is passed through outlet I5 into a conduit 24, which provides an unrestricted passage into a separator 25. (e, At its discharge end 26, conduit 24 is of progresfsively increasing area, and the increase in area is in inverse ratio to the pressure of the pulp, which progressively approaches atmospheric pressure in its' movement toward the discharge end of conduit 24.

. The foregoing arrangement effects a 'velocity control of the pulp, the increased volume permitting suiicient expansion during pressure release to avoid *undue turbulence and accelerated movement of the pulp.

'I'he separator 25 is preferably open to the atmosphere at its upper, end to provide a froth overflow 21, and if desired, a suitable froth crowder may be employed.

1n Figure l the separator is illustrated as having its walls converging toward both ends from its mid-section, and the upper walls thereby function to squeeze the froth across the overflow 21. For convenience in illustration, the separator 25 is shown at substantially the same elevation as the charger I3. In actual practice, it will generally be advantageous to position the separator at a higher elevation than the charge, the difference in elevation being dependent upon the pressure carried in the charger and varying directly with the same. For this reason, the conduit 24 isabroken in the drawings.

The discharge end of conduit 24 is preferably in the mid-section of separator 25 so` that the upper portion of this ing zone 28. AThe part of the separator tank below the'mid-section is a quiescent settling zone 29 through which the gangue material readily passes by gravity.

Inasmuch as certain values may be carried with the gangue toward the bottom of the. tank, a second phase of aeration is provided in the quiescent zone. Air or other gas under pressure is admitted into the lower part of the tank through a distrbtuor 30, preferably in thev form of a lseries of tangential nozzles.

A whirling motion is imparted to the material in the lower portion'of the tank 25, and any values which have descended from the upper frothing zone 28 aresubjected to the" buoyant influence of the gas and are carried up into the frothing zone and yrecovered lin the froth.

Under certain. conditions, it may be desirable to admit water instead of gas through distributor 30, as an example, to Akeep the settling matank constitutes the frothterial from becoming so 'thick that it willvnot A flow readily.

A convenient arrangement for supplying gas to the distributor 30 is to have a conduit 3| connecting the upper side of star feedr I2 with distributor 30. Since the bottom of the star feeder I2 isI exposed to the gas pressure in the upper portion of the charger I3, it follows that as the star revolves, (assuming a counterclockwisel motion), the bottom segment will carrywith it a charge of gas at the pressure in the charger, whichfif not released, will pass upward vinto collector I0, when such segment reaches the upper position, resulting in undesir. able agitation in collector I0.

To avoid this, the inlet to conduit 3l is so @nl ranged that when a gas-carrying segment of the44 feeder reaches an approximate horizontal posiescape through the inlet inwconduit 3 I.

separator which facilitates separation of thel values from the gangue and prevents accumulation of slimes on the separator walls. Return of liquid from separator tank 25 into conduit 3| during the intervals when no gas is flowing is prevented by a check valve 32 which may be of any suitable type. v

Better results are attained in the frothing zone 28, when the liquid is in a state of comparative quiescence and to this end, swirl-restraining baliies 33, preferably in radial arrangement are provided in the mid-section of separator 25.

Gangue material settling by gravity in quiescent zone 29 passes into a sump 34and is thereafter discharged by any suitable means, a star feeder 35 being illustrated as effective for this purpose. l

While I do not wish to be limited to any particular driving assembly, a convenient arrangement has been illustrated in which a shaft 3B suitably journalled in conditioner 5 carries two pulleys 3l and 38 externally of conditioner 5, as

well as the agitators 9 within the same. Pulley-3ll is in driving connection with any suitable power source (not shown).

Pulley 38 is connected by a belt 39 with a pulley 40 on a shaft 4I, which acts as the driving element of speed regulating mechanism I5. The star feeder I2 is in driving connection with mechanism I5 and its rate of rotation is controlled by the iioat mechanism I4, while the rate of rotation of star feeder 35 is varied in proportion to the quantity of gangue to be removed.

The operation will be described in connection with the separation of coal from rock and other material with which it occurs in nature, it being understood that the process is'also adapted for the treatment of various types cf mineralized matter.

The coal is first pulverized to a desired size by any well known method of comminution, for example, to a size which will permit all the pulverized material to pass through a screen of approximately ten meshes per inch.

Water is added as the material is fed into launder 6, or if wet grinding is employed, the water is added before grinding and the pulp is delivered to launder 6.

Ihe coal in liquidA suspension is thoroughly mixed in conditioner 5 with predetermined amounts of reagent. After the `pulp is properly conditioned, it is passed into collecting tank Ill.

The conditioned pulp is admitted from collector I0 into charger I3,by star feeder I2 operating under the control of mechanism I5, the quantity of pulp entering charger I3 being substantially the same as the discharge therefrom. to maintain the liquid level constant.

Pulp in charger I3 is subjected to pressure of a gas, lime kiln gas, for example, admitted simultaneously above and within the liquid body. The

pressure ofthe gas is regulated so that the pressure above the liquid level exceeds the pressure of gas in the liquid body.

As arresult of this condition. quantities of gas are absorbed and caused to go into solution in the liquid body. The gas pressure above the liquid level moves the pulp through discharge outlet I6 whenever valve I1 is opened, and the material under treatment `thereupon .moves freely through conduit 24 and discharges into separator 25.

It wm be understood that once the desired` liquid level has been attained and the gas pres-t sures properly regulated, little, if any, regulation of valve II is required, and the operation thereafter is continuous, subject to a continuous feed.

Asthe pulp approaches the discharge end 26 of conduit 24, the pressure is progressively released, since separator 25 is maintained open to the atmosphene. The conduit 24 is of increasing crossfroth and subsequently removed by overow.

With each 'partial revolution of star feeder I2,

vgas under pressure is delivered to distributor 30 and a swirling motion is imparted to material in the lower portion 29 of the separator tank, and because of the intermittent admission of gas, a pulsating action is produced. Value settling withv gangue are thereby floated and collected with the froth forming at the top of the liquid body. From the foregoing it will be apparent that violent agitation is eliminated and as a result the froth required to collect the values does not have to be as stable as froth in devices employing l violent agitation. Because of the extent of aeration induced by the pressure release, the values are continuously brought in contact with the bubbles rising to the surface. The two factors aforementioned, vmake possible an effective frothing even whenv comparatively small quantities of reagent are used.

The froth overflowing into a froth launder 42 Ion separator 25 is rather brittle alnd in proper of gas than when hot.. For example, waterat 10 C. will dissolve twice as much CO2 as it will dissolvevat 35 C. Hence, if the charger I3 is operated cold, and the pressure release takes place at a higher temperature, a greater evolution of gas ywill result, and an increased frothing action and separation will be attained.

'I'he charger tank I3 illustrated in Figure 2 is similar in all respects to the charger tank I3 of Figure 1, except that constant pressure valves 43 on gas lines 20 and 2I are provided inplace of the automatic. regulating device 23.

Flue gas from` a suitable source is delivered into a heat exchange device 44 through which the conduit 24 extends. heat exchanger 44 and then passed on to a compressor 45, and thereafter the .compressed gases The iiue gas is cooled in the 25, releases large quantities of gas which enhance the frothing action.

In the modification illustrated in Figure 3, preliminary conditioning of the pulp is eliminated, and the pulp is fed directly from launder -6 into collector i0. The charging in this device is identical with the charging illustrated in Figure 1. The absence of reagent from the pulp at this stage of the treatment avoids any preliminary frothing.

As the pulp passes through conduit 24, reagent is introduced therein by a pump 41 or other suitable feeding device, and due to the pressure in the material as it passes through conduit 24, a thorough mixing of pulp and reagent is eifected by the time the material is discharged into separater 25.

Whenever the discharge product passing through sump 34, contains considerable quantities of valuable constituents, it may be desirable to re-treat this product and a convenient arrangement for so doing is illustrated in Figure 4.

The star feeder 35 controlling the discharge Jfrom sump 34, becomes the feeding device for a second charger I3a` and separator 25a, identical in all respects to those elements of the first treatment. Reagent is supplied through a feed pipe 48 before the material reaches the star feeder 35.

In the various modifications, a discharge outlet 49 of the valve-controlled type `can be provided in the bottom of conduit 24, to permit cleaning of the same.

From the foregoing it is apparent that the process may be conveniently practiced in apparatus of a different character than that indicated in the drawings. It is likewise apparent that the methods hereinabove described may be employed in treating various different kinds of solid material in liquid suspension.

Changes and modifications in the various steps and treatments, and arrangement of parts may be availed of within the spirit and scope of the invention as defined in the hereunto appended claims.

What I claim and desire to secure by Letters Patent is:

l. The process of treating solids in liquid'suspension, comprising, confining a body of solids in liquid suspension, introducing gas under pressure into said body beneath the surface thereof, subjecting the body to the action of a pressure gas externally applied, while so confined, and inducing a separation of constituent materials in the body by progressively decreasing pressure on the body until it reaches atmospheric pressure, in a releasing action.

2. 'I he process of treating solids in liquid suspension, comprising, confining a body of solids in liquid suspension, introducing gas under pressure into said body beneath the surface thereof, subjecting the body to the action of a pressure gas externally applied, While so confined, and inducing a separation ofconstituent materials in the body by exposing the body to the atmosphere in a movement at -a progressively reduced velocity.

3. The process of treating solids in liquid suspension, comprising, confining a body of solids in liquid suspension, simultaneously introducing gas under pressure into said body beneath the surface thereof and -externally ofthe same while so confined, to thereby subject the body to compression, and inducing a separation of constituent materials in the body by a subsequent release of pressure on the body in .la movement at a progres-L sively reduced velocityc 4. The process of treating solids in liquid suspension, comprising, confining a body of solids in liquid suspension, simultaneously introducing gas under pressure into said body beneath the surface thereof and externally of the same while so confined, the pressure of the gas externally of. the body being in excess of the pressure of the gas within the same, to thereby subject the body Y to compression, and inducing a separation of constituent materials in the body by a subsequent release of pressure on the body.

5. In a froth flotation process, thesteps of simultaneously cooling a pressure gas being intro-v duced into a pulp under treatment, and heating the pulp in which the gas has previously been introduced after compression byV utilizing heat withdrawn from the cooled gases as the heating medium.

6. The process of coal flotation comprising, mixing a coal-containing pulp with a. flotation agent, subjecting the mixture to compression while introducing a gas under pressure therein beneath its surface, and floating the coal constituentsof the mixture in a froth formed by ref I lease of the pressure on the mixture.

'7. 'I'he process of coal flotation comprising, mixing a coal-containing pulp with a notation agent, subject-ing the mixture to compression while entering a soluble gas under pressure into solutionl beneath its surface, and oatingthe coal constituents of the mixture in a froth formed by release of the pressure `on the mixture.

8. 'I'he process of coall otation comprising, subjecting a coal-containing pulp to compression while introducing a gas under pressure therein beneath its surface, introducing a flotation agent into the compressed pulp, moving the pulp through a zone of'decreasing pressure, and floating the coal constituents of the mixture in a froth formed by release of the pressure on the pulp.

9. In a process of treating solids in liquid suspension, including the treatment of material in intercommunicating aerating and settling zones, the steps of continuously subjecting solids in liquid suspension to the action of an expanding body of gas in the aerating zone, and intermittently subjecting material in the settling zone to the action of an expanding body of gas.

l0. The froth otation process comprising 'charging a pulp with a compressible fluid, comcharging a pulp with a compressible fluid, compressing the charged pulp, inducing a flow of the pulp and a flotation agent to a zone of progressively decreasing pressure, progressively expanding the volume of the pulp in its passage through said zone, discharging the pulp from said zone at approximately atmospheric pressure to induce frothing in the pulp, and maintaining a quiescent zone in the discharged body below the zone of frothing for gravity settling of material not acted on by the frothing.

l2. The froth lflotation process comprising charging a pulp with a compressible fluid, compressing the charged pulp, inducing a flow of the pulp 26nd a dotation 'agent to a zone of progressively decreasing pressure, progressively increasing the volume of the pulp in its passage through said zone, discharging the pulp from said zone at y an elevated point at approximately atmospheric pressure to induce frothing in the pulp, subjecting the discharge pulp to a pulsating action to promote separation, overflowing a concentrate collectedin the f roth at an elevated point of discharge, and removing gangue from the pulpby gravity settling below the zone of frthing.

13. A system of treating solids in liquid suspension, comprising a charging vessel, means for intermittently feeding measured amounts of solids in liquid suspension to said vessel, means for admitting a pressure fluid into said vessel for changing and compressing material fed into the same,

' an open separating vessel having an elevated overiiow and' a .discharge for settled material, means for delivering the charged material from the charging vessel into the separating vessel above its discharge, and at substantially atmospheric pressure to induce aeration by release of pressure on the material, a conduit to receive gas escaping from the charging vessel during each deliverylof feed thereto, and a discharge nozzle disposed in the lower portion of the separating vessel in operative connection withthe conduit for eifecting a pulsating movement of the material settling by gravity in said vessel.

14. A system of treating solids in liquid suspension, comprising a charging vessel, means for intermittently feeding measured amounts of solids in liquid suspension to said vessel,x means for admitting a pressure fluid into said vessel for charging and compressing material fed-into the same, an open separating vessel having an elevated overiiow and a discharge for settled material, means for delivering the charged material from the charging vessel into the separating vessel above its discharge, and at substantially atmospheric pressure to induce aeration by release of pressure on the material, a conduit to receive gas escaping from the charging vessel during each delivery of feed thereto, a discharge nozzle disposed in the lower portion of the separating vessel in operative connection with theconduit for,

effecting a pulsating movement of the material settling by gravity in said vessel, and a valve in the conduit. for preventing the escape of liquid through the nozzle when gas is not flowing through the conduit.

15. Froth flotation apparatus, comprising a charging vessel havinga feed inlet and a discharge outlet, a valve controlling the rate of dischargethru said outlet, a mechanism controlled by the pulp level in the charging vessel for regulation of the rate of pulp feed, means for introducing a pressure gas into the pulp body in the charging vessel, means for introducing gas under pressure into the charging vessel above the liquid level, and a separator chamber in communication with the discharge.

16. Froth flotation apparatus, comprising a Acharging vessel having a feed inlet and a discharge outlet, a valve controlling the rate of discharge thru said outlet, a mechanism controlled by the pulp level in the charging vessel for regulation of the rate of pulp feed, an element for introducing a pressure gas into the charging vessel above and below the liquid level, and a separator chamber in communication with the discharge.

17. A system of treating solids in liquid-suspension, comprising a charging vessel having a controlled discharge determining a liquid level therein, means for feeding measured amounts of solids in liquid suspension to said vessel, means for admitting a pressure fluid into said vessel beneath the liquid level for charging and compressing material fed into the same, a separating vessel communicating with the atmosphere and having an overflow at a higher elevation than the liquid level in the charging vessel and havingia discharge for settled material therebelow, and means for delivering the charged material from the charging vessel into the separating vessel above its dis# charge, in a continuous operation and at substantially atmospheric pressure to induce aeration by release of pressure on' the material.

18. 'I'he improvement in a froth iiotation process in which a pulp and gas are subjected to superatmospheric pressure in one zone and is then discharged into a frothing zone maintained at atmospheric pressure, to induce frothing, which comprises discharging a pulp body subjected to such superatmospheric pressure, into a zone of frothing through a restricted zone of progressively increasing area in amovement of progressively decreasing velocity.

19. 'I'he improvement in a froth flotation process in which a pulp and a gas are subjected to superatmospheric pressure in one zone and isv then discharged into a frothing'zone maintained '-at atmospheric pressure, to induce frothing, which comprises discharging a pulp body subjected to such superatmospheric pressure, into a zone of frothing through a zone in which the pressure on the body progressively approaches atmospheric in a movement of progressively decreasing velocity.

20. In afroth notation process, the steps of compressing a conned body of pulp by simultaneously introducing a gas under pressure into the body of pulp beneath its surface and ex-v teriorly of the same within the zone of confinement, and discharging the compressed body into a frothing zone through a restricted zone of progressively increasing area, in a movement in which the pressure on the body progressively approaches atmospheric.

21. In a. froth flotation process, the steps in a continuous operation, of compressing a pulp body, while subjected to a restricted ilow, by simultaneously introducing a gas under pressure into the pulp body beneath its surface and exteriorly of the same within the restricted zone, and continuously discharging compressed pulp from the restricted zone into a frothing zone in a movement at a progressively decreasing velocity, and' in which pressure on the moving pulp immediately prior toits entrance into the frothing zone is substantially equal to atmospheric pressure.

22. 'I'he froth flotation process which comprises introducing a water-soluble gas into a con- 23. 'I'he froth flotation process which comprises introducing a gas containing carbon dioxide into a confined body of pulp, compressing.

the pulp containing the gas, maintaininga predetermined pulp temperature during .compression at which the gas readily enters into solution. moving the compressed pulp to a discharge in 5 iined body of pulp, compressing the pulp containing the gas. maintaining a predetermined pulp temperatur?.i during compression at which V the gas readily enters into solution, moving the compressed pulp to a discharge in a pressurea heating action eiective for accelerating evolution of gas in the discharging pulp. 25. fIhe process of coal flotation which comprises, mixing a coal-containing pulp with a ilo- 5 tation agent, vintroducing a soluble gas into the release zone, and subjecting the moving pulp to,

pulp beneath its surface, treated to compression, and then iloating coal constituents of the pulp by discharging the coml. pressed pulp into a frothing zone maintained 'at' atmospheric pressure, in a movement of pmgressively decreasing velocity.

26. In a froth flotation process, the step of preparing pulp for a Irothing action by simultaneously introducing gas under pressure exfteribrly of a conned body of pulp and entering such gas into solution in the pulp while maintaining a pressure exteriorly of the body in excess of the pressurewithin the same, during such gas-introducing action.

' JOHN D. PRICE.

subjecting the pulp yio 

